Heap allocate drawing buffer

On some system it seems that the stack is quite small so now we heap
allocate the buffer instead. Also updated the docs and examples using
that instead of being on the stack. Bumped version to 0.2.4

Closes #8

README.md

@@ -12,7 +12,7 @@ Usage
 ```toml
 # Cargo.toml
 [dependencies]
-minifb = "0.2.3"
+minifb = "0.2.4"
 ```
 
 Example
@@ -25,7 +25,7 @@ const WIDTH: usize = 640;
 const HEIGHT: usize = 360;
 
 fn main() {
-    let mut buffer: [u32; WIDTH * HEIGHT] = [0; WIDTH * HEIGHT];
+    let mut buffer: Vec<u32> = vec![0; WIDTH * HEIGHT];
 
     let mut window = match minifb::Window::new("Test - ESC to exit", WIDTH, HEIGHT, Scale::X1) {
         Ok(win) => win,

examples/noise.rs

@@ -1,6 +1,6 @@
 extern crate minifb;
 
-use minifb::*;
+use minifb::{Window, Key, Scale};
 
 const WIDTH: usize = 640;
 const HEIGHT: usize = 360;
@@ -10,7 +10,7 @@ fn main() {
     let mut carry;
     let mut seed = 0xbeefu32;
 
-    let mut buffer: [u32; WIDTH * HEIGHT] = [0; WIDTH * HEIGHT];
+    let mut buffer: Vec<u32> = vec![0; WIDTH * HEIGHT];
 
     let mut window = match Window::new("Noise Test - Press ESC to exit", WIDTH, HEIGHT, Scale::X2) {
         Ok(win) => win,

src/lib.rs

@@ -183,7 +183,7 @@ use self::os::unix as imp;
 /// const WIDTH: usize = 640;
 /// const HEIGHT: usize = 360;
 ///
-/// let mut buffer: [u32; WIDTH * HEIGHT] = [0; WIDTH * HEIGHT];
+/// let mut buffer: Vec<u32> = vec![0; WIDTH * HEIGHT];
 ///
 /// let mut window = match Window::new("Test - Press ESC to exit", WIDTH, HEIGHT, Scale::X1).unwrap()
 ///
@@ -222,7 +222,7 @@ impl Window {
     /// # Examples
     ///
     /// ```ignore
-    /// let mut buffer: [u32; 640 * 400] = [0; 640 * 400];
+    /// let mut buffer: Vec<u32> = vec![0; 640 * 400];
     ///
     /// let mut window = match Window::new("Test", 640, 400, Scale::X1).unwrap();
     ///